β-Cyclodextrin is Used as a Solid-state Electrolyte Additive to Improve the Electrochemical Properties of Zinc-Ion Batteries

Abstract

Solid-state zinc-ion batteries (SSZIBs) have become a promising alternative energy storage system in the field of large-scale energy storage and flexible electronics due to their high safety, low cost, environmental friendliness and excellent theoretical specific capacity. However, there are still bottlenecks such as low ionic conductivity at room temperature, high solid-solid interface impedance, and poor zinc dendrite growth and interface stability. In order to solve these problems, polyethylene oxide (PEO) based solid-state electrolyte was used, and its polymer skeleton structure can inhibit the formation of zinc dendrites. However, PEO-based solid electrolytes still have defects such as insufficient ionic conductivity at room temperature and insufficient interface contact, which need to be further improved by functional additives. With its unique caged supramolecular structure, β-cyclodextrin can form host-guest complexes with zinc ions, significantly improving the ionic conductivity of PEO-based solid electrolytes. In this study, β-CD was introduced into the system as a modified additive, and the optimized β-CD solid-state electrolyte Zn||Zn was used Zn symmetric batteries exhibit an ultra-long cycle life of 675 h at a current density of 10 mA cm^-2 and a capacity density of 1 mAh cm^-2, and an ultra-long cycle life of 813 h at a current density of 4 mA cm^-2 and a capacity density of 1 mAh cm^-2. For Zn||I₂ cell, with an initial discharge specific capacity of about 144.51 mAh g^-1 at a current density of 0.5 A g^-1, still maintains 91% capacity after 1800 cycles. This study not only provides a feasible scheme for zinc anode stabilization, but also confirms that β-CD provides a practical technical path for the practical application of PEO solid-state electrolyte batteries.